The present invention relates to a thermosetting composition, and more particularly to a thermosetting composition suitable for use of top coatings for automobiles, outer walls of buildings, industrial equipments, steel furnitures, household electric appliances, plastics, and the like, especially clear coatings required to have excellent durability and appearance.
Thermosetting coatings which have hitherto been used contain a melamine resin such as an alkyd melamine resin, an acrylic melamine resin or an epoxy melamine resin as a crosslinking agent. Accordingly, there cannot be solved a problem that a bad-smelling caused from the melamine resin remains.
Japanese Unexamined Patent Publication No. 141952/1989 discloses a crosslinking mechanism of a polyol resin and a hydrolyzable silyl group-containing resin, which is quite different from conventional crosslinking mechanism of the polyol resin and the melamine resin.
However, when the mixture of the polyol resin and the hydrolyzable silyl group-containing polymer is used as the coating composition which is required to rapidly cure the coating film without using a catalyst, it is required to heat the film to a high temperature, in other words, a large amount of energy is consumed, because a curing speed of the film of the mixture containing no curing catalyst is slow at room temperature or even if heating it to a relatively low temperature.
Although the above-mentioned defect can be solved by using the curing catalyst together with the mixture of the polyol resin and the hydrolyzable silyl group-containing polymer, such a composition is used as a two-component composition, that is, the curing catalyst is admixed with the mixture just before the use of the composition. Also, Japanese Patent Application No. 70926/1989 discloses that the mixture of the polyol resin and the hydrolyzable silyl group-containing polymer containing the curing catalyst is admixed with a dehydrating agent or an alkyl alcohol, whereby the obtained composition can be used as a one-component composition.
In any case, the above-mentioned compositions are unsatisfactory in storage stability under semi-open conditions.
An object of the present invention is to provide a thermosetting composition which excellent in reactivity as well as stability and appearance.
This and the other objects of the present invention will become apparent from the following description hereinafter.